Skip to main content

Full text of "Flora Indica Vol-I"

See other formats

172                                  FLORA INDICA.
woods, bat there are few ilatural orders of any extent amongst which scandeut genera
are not 'to be found; these have often no further relation to one another than their
scandeut habit, and the woods of nearly-allied species often differ essentially; add to
these, the fact that the wood of erect Exogens sometimes presents as great anomalies
as that of scandent ones, and even in some cases\ imitates the latter, and the value of
the fact in its broadest asjject is considerably diminished,
Menispermacea exhibit very unequally, but always more or less, certain features
common to most scandent plants; as," a spongy stem, abundance of cellular tissue,
and of sclerogen cells in it, laxity of pleurenchyma, irregular development of woody
bundles and liber, absence of rings of annual increase, wood often wholly composed
of dotted, scahriform, or pitted vessels, always accompanied by many of very large
diameter, and lastly, great anomalies in the structure of the pith.
Such characters are more or less common to the allies of Menispermacece, as JCad-
suracetBt Anonactos, and Glematidea, and also 'to plants having no direct affinity with
these or with one another, s Phytocrenete, NqtetitAete, Chlorantkacete, Malpig/tiacea,
dome Santalacea, Balanvphorea, Piperacea, Comlretacea, rerbenacea, Vitis, etc.,
aud some scandent Leyuminosa and Composite. Amongst all these the only re-
cognizable relation between function and structure is, perhaps, the fact that the lax
tissues and abundance of; large air-vessels in the wood, ensure a free circulation of
fluids and gases through vessels which, by reason of the many convolutions aud
contortions to which they are subjected, are peculiarly exposed to constriction.
The prevalence of these peculiarities iu Menisperais suggests three subjects of in-
quiry :1. Do they indicate a high or low position of Jttenispermacea, amongst
JStogeus? 2. Do they indicate a transition to Endogens? 3. Do they betray any
affinity with other natural orders placed at a distance in our systems?
1. At the outset of thje first of these questions, we are met by the inquiry, what
constitutes perfection and imperfection in wood structure, and indeed in the Vegetable
Kingdom generally ? Under the notes that are appended to Ranunculacece, will be
found some on comparative complexity in the floral organs, which are applicable to
Mtmiiperinaeecet and whiph argue their belonging to a low type, But, by a parity of '
reasoning, the same arguments applied to the wood of this Order mny by some be as-
sumed to indicate a highly developed type. In illustration of this, we may remark that
there is much more complexity in the construction of a three years old stem of
Coscinium, than in Magnolia, or most other Exogctis of the same age; for whereas
there is in "most ordinary Exogens an annual repetition of parenchyma and plearen-
chyma, with ifew large vessels, but without change in relative position, and with little
variation in the structure of the component parts of cadi year's growth, we have in
btenispermacece mauy structurally different forms of cellular ar.U vascular tissue an-
nually developed in the stem, besides liber-buudlus, and further, in some, a double
system of Exogenous bundles of wood and'of liber is developed, wholly indepen-
dently of those first deposited:
It may be argued, 'that the great prevalence of parenchyma, and constant irregula-
rities in the development of the various vascular tissues, denote imperfection; when
it will be answered, that during several years the growth of Htfenispermaccit is always
uormnlly Exogenous, that the simplest theoretical plan upon which this could be con-
tinued would be by the annual repetition of the same, and that a deviation from this
type and arrangement implies a modification of structure for another and higher
function; in short, that, in 'the vegetable as in the Animal kingdom, specialization
and complexity ofjwrgan* for the pocformancc of special functions implies relative
elcvatiou in the' scale. It is true t|iat we may not be able to recognize the func-
tion, but in this, as in oU similar cases, we must assume that when a structure is
fully developed, it 'implies the existence of a function in either a latent or active
Decaisue, in his admirable essay on lardiza&alea, has thrown great light upon
the structure of Mcmspermeona wood, and treated the whole subject, in its many
bearings, in a most masterly manner,; he indeed was the first to show the relations
between the ages of the particular organs;and some of the abnormal characters